Preheat oven to 220C/Gas 7.

Boil water for the vegetables.

Finely grate the parmesan for the topping, toss in a small bowl with the breadcrumbs and set aside.

Cut sweet potatoes and butternut squash into quarters. Put into a large pan with boiling water and cover with lid. Cook for 15-20 minutes until tender.

Prepare the herbs. Pick off rosemary leaves and roughly chop with sage. Set aside in a bowl.

Prepare another pot of boiled water for the lasagne. When ready, add a drizzle of olive oil and the lasagne sheets. Cook as directed.

Meanwhile, prepare the sauce by grating parmesan and the ginger after peeling. Put both in a medium bowl, add the ricotta, egg yolks, nutmeg, salt and pepper, mix thoroughly and set aside.

Drain the lasagne sheets. Place back into the pan and add olive oil to ensure that they won't stick together.

Drain the vegetables and mash until smooth. Add salt and pepper to taste.

Assemble lasagne in a baking dish. Use a third of the mashed vegetables as the base layer. Next scatter a third of the herbs, pine nuts, and spinach leaves over the base layer, then arrange 4 lasagne sheets on top, cutting to fit if necessary. Spread a third of the white sauce over. Repeat twice more, giving you three layers. Sprinkle parmesan breadcrumbs on top and bake for 15-20 minutes.